Fission product removal from organic solutions



United States Patent mssIoN PRODUCT REMOVAL FROM ORGANIC "soLU'rroNs Rayinond Moore, Richland, Wash., assignor vto the VUnited States of America as represented by the United YStates Atomic, Energy Commission Y -No Drawing. -f Application November 24 1958 Serial No.116,1s3

13 Claims. (Cl. 26o-461) invention deals "with the decontaminationV of organic solventsfrom fission products and in particular with rthe. treatment of solvents that had been used for the extraction of uranium and/or plutonium from aqueousfacid solutions of neutron-irradiatedruranium.

:Inj extraction processes the uranium and/or plutonium values are usually first extracted into a water-immiscible organicisolvent and. then recovered therefrom bybacle extraction with 4anaqueous medium. The fission products in most instancesremain in the aqueous solution; in othert'yvordsgtheyuate 'not taken up `to a considerable degreeby theorganic solvent. VVHowever, no extraction process accomplishes a quantitative separation and some of the fission product values areex t racted nto'- the organic, solvent and. retained therein4 during back-extraction, lyvithf'thelv aqueous medium, .Since the organic solvent issually recycledv for obvious` economical reasons, it 1becomes more enriched in fission products with each 'cy' c :le .y .Eventually the fission product content becomes process for the removal of fission products from'organic solvents whereby the solvent is regenerated, so that itv can be used again immediately for extraction.

Manganese dioxide Vhas a great affinity for fission products and is therefore ideally'suitable for removing fission products from the organic solutions described above.

certainty.

It has now been found that manganese dioxide that This function as a so-called scavenger is possi' bly due to adsorption, but the type of reaction which is responsible for the scavenging elect is not known with has been prepared from manganese carbonate by heatingv at from 300 to 500 C. has an increased affinity for the' fission products and therefore is more eflicient than` manganese dioxide prepared by other more conventional processes.

It was also found that thecarrying or scavenging elffect of 'manganese dioxide prepared "from manganese carbonate can still be furthermore impovedf by al kaliihgwthe'l'organic solution to' be treated. The steps which `accomplishthis`alkalizing effect willbe described inl-detaill'laterin this'spe'ciiicaticn.'

Finally itf'was also Yfound that, inthe case of ktributyl desirable side product in the .extraction with tributyl'v For many extractionphosphateV Vfrom acid solutions.n o processes the tributylphosphate has to be pretreated by Washing it wither! aqueous Sodium sarbcnate .Orodum rice hydroxide solution to remove the dibutyl phosphate, be-

cause the latter exerts a complexing action'on'many metals, for instance on uranium and thorium. This pretreatment with the 'alkaline solutions is unnecessary in the process of this invention, because the manganese' dioxide accomplishes the same result.

The process of this invention thus broadly comprises heating manganese carbonate in air to a temperature of between 300 and 500f C. whereby manganese dioxide is formed; mixing the manganese dioxide with the lission product-.containing organic solvent .to be vtreated'whereby the iission product values are precipitated on the manganese dioxide; and separating the issionproduct-containing manganese dioxide from the solvent. j

While a temperature range of from M300, Yto 500 C. is

operative for the calcination of the manganese carbonate, the range of vfrom300 to'400 C. vis, preferred. It

was` found that the manganese dioxide prepared at the ylower temperature has a larger surface area. For inv stance, using the YB.E .T. method` (which -is 'a method deviced'byY Brunauer, Emmett andrTellerdcribed, for

instance, in A' Treatise on Physical Chemistry by Taylor and Glasstone, vol. I I, pages 602-605, Van

Nostrand; second printing), it was ascertainedthat man-1f ganese dioxide `-produced -by calcinin'g at 350"-'C. had asurface areaofilS/LZ square meters, while vthatproduced at 500 C. had aY surface area of 54.2 square meters/gram only.

However, either-product was suit able for removing iissionproducts. --`A"heating-time of' from 30 to 6,0.min`utes was usually suiiicient.V

The alkalizationofl the solvent mentioned above can be eithercarried out as a pretreatment with a sodium carbonate solution, for Vinstance of from 3 to 5%, or with a sodium-hydroxide solution, for instance of from 5 to 10%; however, the preferred method of alkalizingv is by adding solid calcium oxide to the solventbefore or together With the manganese dioxide.V `The quantity of the calciumv oxide may range from 3 to 5 pounds per 100 gallons of solvent.

The` effects vof various pretreatment procedures, inl" cluding. that-with nitric acid, are shown in Tables y land II. In all instances the solvents were tributyl phosphate (tLTBPn).

The manganese dioxide for the Vexperiments of Table I had been prepared from'ma'ng'anese carbonate l' In 'liable VI Table l Solution, Pretreatment Pretreat- Scav. :OverlY Final, c./rn./rnl. 1 Reagent ment DF Vall DF c.'/m./ml. t DF Total J Y 4,685.,4 1.0 M HNOa-- 2 05 1.13 2.3` 2,100 4,685.;` 1 0.25M NaiCOs--. 2.9 1.9 5.5V Y r' `869 4,685 10%,NaOH 9. 8 13,1 k128 4,685-- 20% NaOH 3. 5 -l3.2 46.2 4,6631.- 1.0MHNO3 1.8 1.6 2.9 l `1,610 4,663-- 0.25 M NazCOa-- 4. 9 2.7 13. 2 351' 27,300 0.25 M N azCOa.-. 2. 7 140. 3 378 72 27,300 10% NaO 17.3 461 7,980

It will be obviousfrom Table I that nitric acidk is not" a satisfactory pretreating reagent andthat the'mang'anese dioxide, and the decontamination factorv obtained after' nitric `acid treatment is lower than that Yobtained with the i untreated manganese dioxide.`

M1102 prepared by calcination at 350 C.

"MnOa prepared by calculation at 500 C.

YTable II shows that the decontamination factor (fDF=c./m./ml. in feed:c./m./.m1. in treated solution.) of the manganese dioxide is improved fourto fivefold by treatment with solid calcium oxide. This is not as good as the improvement obtained with the alkaline solutions; however, the calcium oxide method has the advantage that it does not require any additional steps, .because it can be added together with the manganese dioxide and separation of an aqueous from an organic phase is not necessary.

Table II also illustrates the removal of dibutyl phosphate. While the dibutyl phosphate in the original solutions ranged from 100 to 200 p.p.m., its content was reduced to almost zero in three runs and to between and 20 p.p.m. in the fourth run.

The quantity of manganese dioxidecan vary widely. The efficiency of the process, however, increases with increasing amounts of manganese dioxide, the rate of increase slowing down abruptly above a quantity .of about 4 grains of manganese dioxide per liter of solution, which corresponds to about 3.3 pounds of manganese dioxide per 100 gallons. This eiect of quantity of manganese dioxide is obvious from data compiled in Table III. The manganese dioxide used there had been prepared by calcination of manganese carbonate at 350 C. scavenging was carried out in these runs at a temperature of 50 C., and contact `between the manganese dioxide and the or- Table I V TBP-solution, Temp., Scav. Bcav. Scav. Over-all c./n1./n.1l. C. DF. DF F,

Total l zr-Nb R11-Rh Total y 25 1. 9 (i) 5. 4 3. 5 3.v 3 (2) 11.19 70 3.8 4. 1 "11. 0 25 2. 7 (2) (2) 13. 3 70 7. 2 9. 2 -4 34. 8 25 l 2. 2 (9) 2. 0 1.21. 6 70 1 3. 7 100 4. 5 l 37. 1 110 l 419 100 8. 9 1 4B. 9

1 Presence of 1131 not removed byscavengingprecludes direct comparison of these numbers with those above.

2 Was not determined.

After the treatment of the organic solution with the manganese dioxide, which then contains the ssion product values, the manganese dioxide 4is removed from .the solution by any known methods, for instance bycentrifugation, ltration or decantation, or any combination ,of these means.

The process does not require any specic equipment. Any device known to those skilled in the art .is suitable. The use of a mixing device is especially advantageous to intensify contact between the solid manganese dioxide and the organic solution. The process can be carried out in a continuous manner or as a batch process.

lt will be understood that this invention is not-to be limited to the details given herein, but that it maybe modified within the scope vof the appended claims.

What is claimed is:

l. A process of removing fission yproduct Ivalues from an organic extraction solvent, comprising calcining manganese carbonate in air at from 300 to 500 C. whereby manganese dioxide is formed; alkalizing the organic solvent; mixing the manganese dioxide with the solvent whereby the ssion products are carried `on saidmanganese dioxide; and separating the iission-product-containing game solution was maintained for 30 minutes. 40 manganese dioxide from the depleted solvent.

Table III Total Zr-Nb, R11-Rh, 1m, Wt. Alkallzing Procedure of TBP Solution Iy/inJml. 'y/mJml. y/m./m1 y/mJml. MnOa,

2 equal v01, 3% Nazooa Washes 1, 008 1. 6 104 2. 4x10a None None Do 579 1. 5x104 2. 4 1m None o. 5 481 1.1 1o4 1. o 1o3 None 1. o 343 7. 5 1os 1. o 103 None 2. o 32o 6. 9x103 1. 0x103 None 4. u 292 4. 9x10@ 1. 0x10s None 12. 0 351 7. 5X103 2. 4)(103 None None 143 3. 8X103 9. 7X102 None 0. 5 109 1. 9x103 7. 3 1o2 None 1. o a. 1x103 9. s io2 None 2. o 1. 0 1o3 1. 0x102 None 4. o 5, 251 5. 1 1o4 1. 5x104 2. 0x104 Non@ 3, oas 1. 6x104 3. 4x10@ 1. 9 io4 1. 0 2, 999 1. 1 1o4 a. 7 1o3 2. 2x104 2. o 2, 775 6. 9 1o3 a. 7 1oa 2. 2 io4 4. o 3, 205 i. 2 1o4 s. oxioa 1. 6 1o4 None 2, 259 1.9 10 3. 3x10a 1. 9x104 1.0 2. 175 1. 0 10= 2. 2 1o 1. 5x104 2. o 2, 106 1. o 1o= 3. 2x10s 2. o 1o4 4. 0

From the data of Table III is was deduced that a quantity of from 1 to 3.5 pounds of manganese dioxide per 100 gallons of solution represented the optimal conditions.

The process can be carried out at room temperature, as has been shown; however, improved results were obtained at a temperature between 50 and 70 C. The yeffect of elevated temperature is shown in the experiments summarized in Table IV. In these experiments 12 grams of manganese dioxide (calcination'temperature 350 C.) were used per liter of solution. The organic solutions had been washed twice with two equal volumes o a 3% sodium carbonate solution. The over-all dccontamination factors include the eiect of this washing treatment.

2. The process of claim 1 wherein the solvent is tributyl phosphate.

3. The process of claim 1 `wherein the calcinationitemperature ranges between 300 and 400 1C.,

4. The process of claim 1 wherein manganese'dioxide is `adniixed in a quantity of from -1 to -3.'5 pounds per 100 gallons of organic solution.

5. The process of claim 1 wherein mixing iscarried out at a temperature of between 50 and 70 C.

.6. The process of claim 1 wherein alkalizing isfcarried out by contact with an aqueous sodium carbonate solution.

7. The process of claim 6 wherein fthesodium carbonate solution ,has a .concentration of between 3 and,5%.

8. The process of claim 1 wherein alkalizing is carried out by contacting with an aqueous sodium hydroxide solution.

9. The process of claim 8 wherein the concentration of the sodium hydroxide solution ranges between and 10%.

10. The process of claim 1 wherein alkalizing is carried out by the addition of solid calcium oxide to the organic solvent. p

11. The process of` claim 10 wherein the calcium oxide is added in a quantity of from 3 to 5 pounds per 100 gallons of solvent.

12. The process of claim 10 wherein the calcium oxide is added to the organic solvent simultaneously with the manganese dioxide.

13. A process ofV removing fission product values from a solution in dibutyl-phosphate-containing tributyl phosphate, comprising calcining manganese carbonate in air at from 300 to 400 C. whereby manganese dioxide is formed; heating the tributyl phosphate solution to a temperature of between and 70 C.; addingV from 1 to 3.5 pounds of said manganese dioxide and from 3 to 5 pounds of solid calcium oxide each per gallons 'of tributyl phosphate solution, whereby dibutyl phosphate and fission product values are taken up by the manganese dioxide; and separating said manganese dioxide from the tributyl phosphate solution.

References Cited in the le of this patent UNITED STATES PATENTS Wilson Aug. 12, 1958 

1. A PROCESS OF REMOVING FISSION PRODUCT VALUES FROM AN ORGANIC EXTRACTION SOLVENT, COMPRISING CALCINING MANGANESE CARBONATE IN AIR AT FROM 300 TO 500*C. WHEREBY MANGANESE DIOXIDE IS FORMED, ALKALIZING THE ORGANIC SOLVENT, MIXING THE MANGANESE DIOXIDE WITH THE SOLVENT WHEREBY THE FISSION PRODUCTS ARE CARRIED ON SAID MANGANESE DIOXIDE, AND SEPARATING THE FISSION-PRODUCT-CONTAINING MANGANESE DIOXIDE FROM THE DEPLETED SOLVENT. 